1. Field of the Invention
This invention relates generally to a semiconductor technique and more particularly to a method for forming on a semiconductor substrate a silicon-containing insulation film having low film stress by using a plasma CVD (chemical vapor deposition) apparatus.
2. Description of the Related Art
As semiconductors have progressed to accommodate a demand for high speed and high density in recent years, a reduction of capacitance between lines is required to avoid signal delays in the multi-layer wiring technology field. Because a reduction in the dielectric constant of a multi-layer wiring insulation film is required in order to reduce the capacitance between lines, insulation films having low dielectric constants have been developed.
Conventionally, a silicon oxide (SiOx) film is formed by adding oxygen (O2), nitric oxide (NO) or nitrous oxide (N2O) as an oxidizing agent to a silicon source gas such as SiH4 and Si(OC2H5)4 and applying heat or plasma energy to the source gas. A dielectric constant (ε) of this film was approximately 4.0.
If a source gas having two alkoxy groups is used, the dielectric constant of a resulting film can be lowered. For example, by using (CH3)2Si(OCH3)2 as a source gas, a siloxan polymer film having a dielectric constant of 3.0 or lower can be formed by plasma polymerization.
However, films having a dielectric constant of 3.0 or lower have high film stress such as 70 MPa. Because a semiconductor device has multiple layers, if insulation films have high film stress, the adverse effect becomes significant. As a result, such a semiconductor device may not function as is designed. Thus, a reduction of film stress is required.